By Robynn Andracsek, P.E., Burns & McDonnell and Contributing Editor
Beginning July 1, 2011, greenhouse gases (GHGs) alone can make a source major for the Prevention of Significant Deterioration (PSD) program. If your facility is classified as PSD program minor source before the Tailoring Rule you’ll want to stay that way. You’ve probably asked yourself, “Can I stay PSD minor, and if so, how?” The short answer is yes. The long answer (you knew there was a long answer) depends on the magnitude of your actual emissions and on your potential-to-emit.
Coal-fired boilers can skip right over this topic; they are PSD major. However, staying minor is a crucial matter for simple cycle turbine facilities. Many of these facilities were constructed with specific limits on operation to keep their emissions under 250 tpy for each criteria pollutant (simple cycle turbines are not on the “list of 28 source types” in 40 CFR 52.21). This was done knowing that they would have limited operation to provide peaking power.
A quick review of the regulation first. GHGs are subject to regulation at an “existing stationary source that emits or has the potential to emit 100,000 tpy CO2e, when such stationary source undertakes a physical change or change in the method of operation that will result in an emissions increase of 75,000 tpy CO2e or more.” Remember that for PSD, CO2e is measured in English short tons, not metric tons.
Regardless of your situation specifics, the Tailoring Rule and the Mandatory Greenhouse Gas Reporting Rule make it important to know your greenhouse gas emissions in mass, equivalents, English, metric, and so on. Table 1 is my suggestion of the information you need to calculate.
If you are PSD minor but your actual existing carbon dioxide equivalent (CO2e) emissions are over 100,000 tpy, CO2e becomes a regulated pollutant when you make a modification that increases CO2e more than 75,000. With this increase, the source will become PSD major. Therefore, in order to stay PSD minor, you must take limits to keep each modification under 75,000 tpy CO2e.
If you are PSD minor and your potential-to-emit is over 100,000 tpy CO2e but your actual emissions are below 100,000 tpy CO2e, then you have two options to stay PSD minor. You can either take a limit now to keep your potential-to-emit less than 100,000 tpy CO2e or you can wait until you modify the source to limit each project to less than 75,000 tpy CO2e. This works since CO2e is not a regulated pollutant until you meet both conditions: namely, an existing potential-to-emit of 100,000 tpy CO2e and a modification of greater than 75,000 tpy CO2e.
Building a new PSD minor facility is more straightforward but also more stringent. Your potential-to-emit must be less than 100,000 tpy for CO2e and less than 250 tpy or 100 tpy for all other criteria pollutants (NOx, CO, PM10, PM2.5, VOC, and SO2). The difference between having a threshold of 250 tpy or 100 tpy is whether or not your facility type is a “listed” source category (see 40 CFR 52.21(b)(1)(iii)).
An initial increase might be subject to PSD when a subsequent, identical increase isn’t. A new facility with 120,000 CO2e and 50 tpy NOX trips PSD for both pollutants. However, a subsequent increase at this facility of 50 tpy NOX does not trip PSD. Why?
The facility’s PTE is greater than 100,000 tpy CO2e but since emissions will not increase by 75,000 tpy CO2e, GHGs are not “subject to regulation” at the time of the modification. PSD applies to neither GHGs or NOX because while the increase in NOX is above its 40 tpy significance level, the modification is not subject to PSD for GHGs and tht total NOX emissions are below the “major” level of 100 or 250 tpy.
PSD is a confusing and complex program. If you can avoid it by staying PSD minor, do so. It’ll make the PSD major facilities green with envy.
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